A New Approach for Reliable Estimation of Hydraulic Fracture Properties Using Elliptical Flow Data in Tight Gas Wells

Abstract

Summary Gas wells in low-permeability formations usually require hydraulic fracturing to be commercially viable. Pressure transient analysis in hydraulically fractured tight gas wells is commonly based on analysis of three flow regimes: bilinear, linear, and pseudoradial. Without the presence of pseudoradial flow, neither reservoir permeability nor fracture half-length can be independently estimated. In practice, as pseudoradial flow is often absent, the resulting estimation is uncertain and unreliable. On the other hand, elliptical flow, which exists between linear flow and pseudoradial flow, is of long duration (typically months to years). We can acquire much rate and pressure data during this flow regime, but no practical well test analysis technique is currently available to interpret these data. This paper presents a new approach to reliably estimate reservoir and hydraulic fracture properties from analysis of pressure data obtained during the elliptical flow period. The method is applicable to estimate fracture half-length, formation permeability, and skin factor independently for both infinite- and finite-conductivity fractures. It is iterative and features rapid convergence. The method can estimate formation permeability when pseudoradial flow does not exist. Coupled with stable deconvolution technology, which converts variable production-rate and pressure measurements into an equivalent constant-rate pressure drawdown test, this method can provide fracture-property estimates from readily available, noisy production data. We present synthetic and field examples to illustrate the procedures and demonstrate the validity and applicability of the proposed approach.

Integration of microseismic and other post-fracture surveillance with production analysis: A tight gas study

“…The straight-line approach has been used by Economides et al (1994), Wattenbarger et al (1998), Poe et al (1999), and Hager and Jones (2001) for analyzing transient flow; the flowing material balance (FMB) method is an example of a straight-line method that is applicable to the boundary-dominated flow regime and may be used to obtain hydrocarbon-in-place estimates (Palacio and Blasingame, 1993;Doublet et al, 1994;Mattar and McNeil, 1997;Agarwal et al, 1999;Mattar and Anderson, 2005). Very recently, a straight-line method was introduced to analyze the elliptical flow regime (Cheng et al, 2009). 3.…”

“…Straight-line techniques for analyzing transient production data associated with vertical, hydraulically-fractured wells have also been discussed in the literature (see Economides et al, 1994;Poe et al, 1999;Hager and Jones, 2001;Cheng et al, 2009). Application of these techniques for analyzing production data associated with multi-fractured horizontal wells has only been briefly reviewed.…”

“…Rate-normalized Dm(p) function and bilinear, linear and radial superposition time functions are used to account for variable rates and flowing pressures. The elliptical flow regime analysis procedure was developed recently by Cheng et al (2009), and is iterative; separate iterative procedures were developed for wells with infinite-conductivity and finite-conductivity fractures. In the finite-conductivity case, A and B are modified, and bilinear flow regime analysis is also required.…”

Analytical solution and mechanisms of fluid production from hydraulically fractured wells with finite fracture conductivity

“…This is particuarly true when the pressure diffusion in the reservoir is very slow, such as in a low-permeability medium like a shale formation. Steady-state solutions are often used to construct approximate solutions to transient productions in these situations [19,39]. Thus, an analytical steady-state solution remains a useful tool not only for the purpose of elucidating the physical mechanism of fluid production but also for constructing approximate solutions of practical use.…”

Analytical and numerical solutions on the response of pore pressure to cyclic atmospheric loading: with application to Horonobe underground research laboratory, Japan

“…Li et al (2009a) proposed a coupled inversion method to identify formation properties of Horonobe URL by bridging satellite monitoring and characterization of subsurface flow. Cheng et al (2009) presented an approach to reliably estimate reservoir and hydraulic fracture properties from analysis of pressure data obtained during the elliptical flow period. The proposed method is applicable to estimate fracture half-length, formation permeability, and skin factor independently for both infinite-and finite-conductivity fractures.…”